One document matched: draft-ietf-enum-void-01.txt
Differences from draft-ietf-enum-void-00.txt
ENUM R. Stastny
Internet-Draft Oefeg
Expires: November 10, 2005 L. Conroy
Siemens Roke Manor Research
May 9, 2005
IANA Registration for Enumservice VOID
<draft-ietf-enum-void-01.txt>
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Copyright (C) The Internet Society (2005).
Abstract
This document registers the Enumservice 'void' using the URI schemes
'mailto:' and 'http:' as per the IANA registration process defined in
the ENUM specification, RFC3761. This Enumservice may be used to
indicate that the E.164 number (or E.164 number range) tied to the
domain in which the enclosing NAPTR is published is not assigned for
communications service. When such an indication is provided, an ENUM
client can detect calls that will fail "early".
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The Problem . . . . . . . . . . . . . . . . . . . . . . . . 5
4. The Proposed Solution . . . . . . . . . . . . . . . . . . . 6
5. ENUM Service Registration - VOID . . . . . . . . . . . . . . 7
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1 Normative References . . . . . . . . . . . . . . . . . . 13
10.2 Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . 15
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1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, [1].
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2. Introduction
The Circuit Switched Network (CSN) of which the Public Switched
Telephone Network, Integrated Services Digital Network, and Public
Land Mobile Network are part is designed to use E.164 numbers E.164
[2] as native global addresses. If a potential caller has an E.164
number, then to place a call using this address has needed a way to
pass the request either directly or indirectly to systems "in" the
CSN for them to forward.
ENUM has introduced a mechanism to find other contact addresses when
given an E.164 number. Thus, if the caller (or an agent somewhere in
the call path) has access to the global DNS, they can use ENUM
RFC3761 [3] to find alternative contacts to the E.164 number and
place the call using whatever system was indicated in those contacts.
However, ENUM entries may not exist for a given E.164 number for two
reasons. Either the assignee who is entitled to register an ENUM
domain associated with the E.164 number they hold has chosen not to
request this registration, or the number is not currently assigned
for communications service.
In either situation, the caller has no other information and so no
alternative to placing the call via the system that uses E.164
numbers as global identifiers; at present, this is the CSN.
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3. The Problem
At present, from the ENUM client's perspective, two possibilities
exist: there is an ENUM domain that potentially holds alternative
contacts, or there is no ENUM domain, in which case a query on ENUM
will return a DNS response showing 'no such domain' (NXDOMAIN, code
3)[4].
This latter response is ambiguous. There are two potential reasons
for the lack of an ENUM domain holding alternative contacts; either
the assignee has chosen not to register the domain, or the E.164
number is not assigned for communications service at present.
If the number is assigned, then the caller can use the E.164 number
to place the call via a network that uses such identifiers as global
addresses (i.e. the CSN). If however, there is no domain because the
associated E.164 number is not assigned for communications service,
then any attempt to place the call via the CSN will fail.
What would be useful is a mechanism "between" a registration holding
NAPTRs with URIs and the lack of a domain registration. In this way,
an entity who is responsible for E.164 numbers in a range can
indicate that a particular number has not been assigned to anyone for
communications service. For example, if a communications service
provider has been allocated responsibility for delivering calls to
endpoints identified with E.164 numbers in a block, then they may
have some numbers in that block that are currently unused. These
E.164 numbers are not used to terminate calls to end users.
An originating user agent cannot differentiate this state from the
one in which there is an end user as a number assignee, but that end
user has have chosen not to "publish" other contacts. In effect, it
would be more useful if the originating end user could receive a
response that states "there is no service via this number", as
opposed to "there may be service via this number, but there are no
alternative contacts available".
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4. The Proposed Solution
We propose an explicit indication of this "number unassigned" state.
This uses a NAPTR in the "enclosing" zone, with an Enumservice called
VOID that should be taken as an assertion that the associated E.164
number is not assigned to an end user for communications service;
it's an unused number.
This NAPTR can also be used by a National Regulatory Authority (NRA)
to indicate number blocks that it has reserved or has not allocated,
or has not assigned to a service provider.
It is a matter for individual Countries whether or not they will
support (or require) information giving the identity of the current
"owner" of an E.164 number within their responsibility to be made
available via IRIS/Whois. Thus it may not be possible to use these
protocols to find out the entity responsible for a number or number
range, particularly where that number or range is not currently "in
use".
For this reason, we propose that the VOID indication also includes a
contact address (an email address or a web address) by which the
authority responsible for this number (or range) can be contacted.
This may not be the same entity as the one that maintains the DNS
service for that "enclosing zone"; often the NRA will sub-contract a
Registry Operator to maintain the DNS, but it is the NRA who is the
authority for the E.164 number range, not that Registry Operator.
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5. ENUM Service Registration - VOID
Enumservice Name: "VOID"
Enumservice Type: "void"
Enumservice Subtypes: "mailto", "http", "https"
URI Schemes: "mailto:", "http:", "https:"
Functional Specification: The proposed solution in Section 4.
Definition of expected action:
If a NAPTR with this Enumservice is received, it indicates that
the queried E.164 number is currently unassigned to an end user
for communications service.
The recipient SHOULD treat this response as if they had received a
"number not in service" indication from a terminating network.
Note that, whatever subtype exists for this Enumservice, the
generated URI is not a potential target for any current call.
This contact (mailto:[5], http:[6], or https:[7]) MUST NOT be used
in normal call processing but only if there is a non-call related
reason to contact the number holder or authority.
Security considerations: see Section 7.
Intended usage: COMMON
Authors
Lawrence Conroy, Richard Stastny (for authors contact details see
Authors' Addresses section).
Any other information that the author deems interesting:
There are three possible subtypes (each with an associated URI
scheme). In the first case, the subtype is "mailto" and has a
generated URI scheme of "mailto:". This can be used to hold an
email address of the entity responsible for the unassigned number
or number range (such as the NRA, or the Communications Service
Provider or CSP to whom they have allocated a block of numbers, of
which the current number is unused).
The second case has a sub-type of "http" and has a generated URI
scheme of "http:". The last case has a sub-type of "https" and an
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associated generated URI scheme of "https:". In both these, the
URI can be used to indicate a web site holding information on the
number (or number range) associated with the domain holding this
NAPTR. They differ only in whether or not the URL "points to" a
web site using either a standard or TLS-secured connection.
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6. Examples
1. VOID:mailto
$ORIGIN 0.6.9.2.3.6.1.4.4.e164.arpa.
3.8.0 NAPTR 10 100 "u" "E2U+void:mailto"
"!^.*$!mailto:num-drama-info@nra.foo!"
This indicates that the controller of the number block
+441632960xxx does not provide telephony service via the number
+441632960083; it is not assigned to an end user. Information on
the status of this number may be obtainable by contacting the
email address held in the regexp field.
2. VOID:http and VOID:https
$ORIGIN 0.6.9.2.3.6.1.4.4.e164.arpa.
4.8.0 NAPTR 10 100 "u" "E2U+void:http"
"!^.*$!http:\/\/www.nra.foo\/drama-numbers\/index.html!"
$ORIGIN 0.6.9.2.3.6.1.4.4.e164.arpa.
4.8.0 NAPTR 10 100 "u" "E2U+void:https"
"!^.*$!https:\/\/connect.nra.foo\/drama-numbers\/secure.html!"
Both of these examples indicate that the controller of the number
block +441632960xxx does not provide communication service via
the number +441632960084; it is not assigned to an end user.
Information on the status of this number may be obtained by
making an HTTP connection to the web URL shown in the regexp
field of the former example, or making a connection using TLS to
the secure web URL held in the regexp field of the latter
example.
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7. Security Considerations
DNS does not make policy decisions about the records that it shares
with an inquirer. All DNS records must be assumed to be available to
all inquirers at all times. The information provided within an ENUM
record set must therefore be considered to be open to the public.
An analysis of threats specific to the dependence of ENUM on the DNS,
and the applicability of DNSSEC [8] to these, is provided in [9].
The specific issues applicable to this registration are:
1. by including an email address, the responsible authority is
making this available globally. They should expect that the
published email address will be used to send unsolicited
commercial email to them.
2. by publishing the email address, they expose the identity of the
entity that has authority over this E.164 number (or range of
numbers). This may also be the case if a web URL is used.
3. by constructing a DNS response holding a VOID NAPTR, a third
party could initiate a denial of service attack on the assignee
of a number (or number range). The recipient of a "spoofed"
response would react by assuming that the associated E.164 number
is not in service, so denying calls to that number.
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8. IANA Considerations
This document requests registration of the "void" Enumservice with
three sub-types (void:mailto, void:http and void:https) according to
the guidelines and specifications in RFC 3761 [3] and the definitions
in this document.
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9. Acknowledgments
Thanks to Jim Reid for the substantial inputs regarding the mechanism
to query the enclosed zone and to Patrik Faltstrom and Michael
Mealling for their feedback, and colleagues in ETSI TISPAN who helped
to clarify VOID's operational features during the development of
[10].
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10. References
10.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[2] ITU-T, "The International Public Telecommunication Number Plan",
Recommendation E.164, May 1997.
[3] Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource
Identifiers (URI) Dynamic Delegation Discovery System (DDDS)
Application (ENUM)", RFC 3761, April 2004.
[4] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES",
RFC 1034, November 1987.
[5] Hoffman, P., Masinter, L., and J. Zawinski, "The mailto URL
scheme", RFC 2368, July 1998.
[6] Fielding, R. and et al. , "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
[7] Rescola, E., "HTTP over TLS", RFC 2818, May 2000.
10.2 Informative References
[8] Arends, R. and et al. , "Protocol Modifications for the DNS
Security Extensions", RFC 4035, March 2005.
[9] Atkins, D. and R. Austein, "Threat Analysis of the Domain Name
System (DNS)", RFC 3833, August 2004.
[10] ETSI, "Minimum Requirements for Interoperability of ENUM
Implementations", ETSI TS 102 172, January 2005.
[11] Bradner, S., "The Internet Standards Process -- Revision 3",
RFC 2026, BCP 9, October 1996.
[12] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC 3978,
March 2005.
[13] Bradner, S., "Intellectual Property Rights in IETF Technology",
BCP 79, RFC 3979, March 2005.
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Authors' Addresses
Richard Stastny
Oefeg
Postbox 147
1103 Vienna
Austria
Phone: +43-664-420-4100
Email: Richard.stastny@oefeg.at
Lawrence Conroy
Siemens Roke Manor Research
Roke Manor
Romsey
United Kingdom
Phone: +44-1794-833666
Email: lwc@roke.co.uk
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